Head assembly for use in a rotary head extruder for extruding a food product

ABSTRACT

A head assembly ( 10 ) is provided for use in a rotary head extruder ( 12 ) for extruding a food product. The head assembly ( 10 ) includes an annular-shaped stator plate ( 20 ) and a rotating blade plate ( 22 ). The blade plate ( 22 ) preferably includes at least six blades, each with a wedge shaped profile, and the stator plate ( 20 ) includes extrusion channels that extend at an angle in the range of 20°-50° from tangent to a circle defined by an inner surface ( 30 ) of the plate ( 20 ).

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. Ser. No. 12/510,870, filedJul. 28, 2009, the disclosure of which is hereby incorporated byreference.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

MICROFICHE/COPYRIGHT REFERENCE

Not Applicable.

FIELD OF THE INVENTION

This invention relates to extruders for extruding food product, and moreparticularly, to rotary head extruders wherein the food product isextruded radially outward between a pair of plates where one rotatesrelative to the other which is stationary.

BACKGROUND OF THE INVENTION

Rotary head extruders for extruding a food product are known and utilizehead assemblies that include a stationary plate having extrusionchannels and a rotating blade plate having a flat annular face surfacethat rotates past the extrusion channels and three blades that force rawfood product radially outward into the extrusion channels where the foodproduct is gelatinized under pressure and heat and extruded radiallyoutward to form an extruded food product. Such machines have commonlybeen employed for making Cheetos® food snacks and have been in existencesince the 1930's. Over the years there have been numerous attempts toimprove the output capacity of such rotary head extruders but with nosignificant success. Accordingly, there is a continuing need to improvethe output capacity of such machines.

SUMMARY OF THE INVENTION

In accordance with one feature of the invention, a head assembly isprovided for use in a rotary head extruder for extruding a food product,the rotary head extruder including a feed screw mounted for rotationabout an axis to direct raw food product to the head assembly forextrusion thereat. The head assembly includes an annular-shaped statorplate having a plurality of circumferentially spaced extrusion channelsextending outwardly from a radially inner surface centered on the axis;and a rotating blade plate including a plurality of circumferentiallyspaced blades located to extend into an annular space underlying theextrusion channels and the radially inner surface of the stator plate.

In one feature, there are at least six of the circumferentially spacedblades. In a further feature, there are at least ten of thecircumferentially spaced blades. In yet a further feature, there are atleast twelve of the circumferentially spaced blades.

According to one feature, each of the blades has a circumferential widthWC, and the circumferential spacing from one blade to the next is in therange of 0.7 to 1.5 times the width. WC.

As one feature, each of the blades has a wedge-shaped profile thatdiverges from a leading edge to a trailing edge.

In one feature, the head assembly further includes an impeller locatedon the end nose of the feed screw for rotations therewith and surroundedby the stator plate, the impeller including asset of impeller vanes;each of the vanes having a planer face transverse to the axis.

According to one feature, the head assembly further includes an impelleron the rotating blade plate surrounded by the blades, the impellerincluding a set of impeller vanes, each of the vanes having a planerface transverse to the axis.

As one feature, the head assembly further includes: a first impellerlocated on the end nose of the feed screw for rotations therewith andsurrounded by the stator plate, the first impeller including a first setof impeller vanes, each of the vanes of the first set having a planerface transverse to the axis; and a second impeller on the rotating bladeplate surrounded by the blades, the second impeller including a secondset of impeller vanes, each of the vanes of the second set having aplaner face that extends parallel to the faces of the first set ofvanes.

In one feature, the annular-shaped stator plate includes a plurality ofguide walls defining the extrusion channels, each of the guide wallsextending at an angle in the range of 20°-50° from tangent to a circledefined by the inner surface. As a further feature, the angle is in therange of 30°-40°.

As one feature, the stator plate includes a plurality of guide walldefining at least fourteen of the extrusion channels.

In accordance with one feature of the invention, a head assembly isprovided for use in a rotary head extruder for extruding a food product.The rotary head extruder includes a feed screw mounted for rotationabout an axis to direct raw food product to the head assembly forextrusion thereat. The head assembly includes an end nose located on thefeed screw for rotation therewith, and a rotating blade plate. The endnose has an outwardly facing cylindrical surface, and the blade platehas a plurality of circumferentially spaced blades located to extendover the cylindrical surface of the end nose, with each of the bladeshaving a leading edge spaced from the cylindrical surface by a radialdistance in the range of 0.0625-1.000 inches.

Other objects, features, and advantages of the invention will becomeapparent from a review of the entire specification, including theappended claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a somewhat diagrammatic section view of the head assembly fora rotary head extruder embodying the present invention;

FIG. 2 is a view taken along line 2-2 in FIG. 1, but not showing a feedscrew component of the assembly;

FIG. 3 is a view similar to FIG. 2, but showing only a rotating bladeplate of the assembly; and

FIG. 4 is a view taken from line 4-4 in FIG. 1, but showing only thestationary plate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A head assembly 10 is provided for use in a rotary head extruder 12(only partially shown in the drawings) for extruding a food product. Therotary head extruder 12 includes a feed screw 14 mounted for rotationabout an axis 16 to direct raw food product to the head assembly 10 forextrusion thereat, as shown by arrows “A”. The feed screw 14 includes anend nose 17, preferably having an outwardly facing cylindrical surface18 with a reduced outside diameter D relative to the minor diameterD_(m) of the screw threads 19 of the feed screw 14. In one preferredembodiment, the feed screw has six thread leads, with the screw threads19 having a major diameter D_(M)=8.92 inches, a minor diameterD_(m)=8.48 inches, and a reduced outside diameter D=7.75 inches.

The head assembly 10 includes an annular-shaped stator plate 20 and arotating blade plate 22 that is preferably mounted for rotation aboutthe axis 16 in a direction counter to the rotation of the feed screw 14.Preferably, a nose impeller 24 is located on the end nose 17 of the feedscrew 14 for rotation therewith about the axis 16, and another noseimpeller 26 is located on the rotating blade plate 22 for rotationtherewith about the axis 16.

As best seen in FIGS. 1 and 4, the stator plate 20 includes a plurality(18 in the illustrated embodiment) of circumferentially spaced,outwardly opening extrusion channels 28 extending from a radially innersurface 30 that is generally cylindrical and centered on the axis 16 toa radially outer surface 32 that is generally planar and transverse tothe axis 16. As best seen in FIG. 4, the inner surface 30 may include anumber of axially extending grooves 34 such as are employed on at leastsome conventional head assemblies. A plurality of guide walls (again 18in the illustrated embodiment) 36 are provided between the extrusionchannels 28 and, together with a conical surface 38 best seen in FIG. 1,define each of the extrusion channels 28. Preferably, each of the guidewalls extends at an angle a in the range of 20°-50° from tangent to acircle centered on the axis 16 and defined by the inner surface 30. In ahighly preferred embodiment, the angle a is in the range of 30°-40° fromtangent and in a very preferred embodiment the angle a is 33°.

As best seen in FIG. 1, the stator plate 20 can be provided as a faceplate 39 that is fixed to a backer plate 40 with the face plate 39 beingmade from a suitable material, such as brass, ceramic, or cast iron andthe backer plate 40 being made from a suitable material, such as steel.In this regard, the heat conduction properties of the face platematerial are important.

As best seen in FIGS. 1 and 3, the rotating blade plate 22 includes aplurality (12 in the illustrated embodiment) of circumferentially spacedblades 42 located to axially extend into an annular space 44 underlyingthe inner surface 30 and extrusion channels 28 of the stator plate 24and overlying the cylindrical surface 18 of the end nose 17. The blades42 operate to force raw food product that has been delivered to theannular space 44 by the feed screw 14 radially outward into theextrusion channels 28. As best seen in FIGS. 2 and 3, each of the blades42 preferably has a wedge-shaped profile that diverges from a leadingedge 46 to a trailing edge 48. As best seen in FIG. 3, each of theblades 42 has a circumferential width WC from the leading edge 46 to thetrailing edge 48, with a circumferential spacing S from the leading edge46 of one blade 42 to the trailing edge 48 of next blade 42 preferablybeing in the range of 0.7 to 1.5 times the width WC, and in highlypreferred embodiments, the circumferential spacing from one blade 42 tothe next is in the range 0.85 to 1.125. In the illustrated embodiment,the circumferential spacing from one blade to the next is about 0.85times the width WC.

Preferably, as best seen in FIG. 3, a radially inner, planar surface 50of each of the blades 42 extends along a line tangent to an imaginarycircle on which the leading edge 46 lies so that the leading edge 46 ofeach blade 42 is located radially inward from the remainder of the blade42. In this regard, as best seen in FIG. 1, it is preferred that theradial distance R_(G) between each of the edges 46 and the cylindricalsurface 18 of the end nose 17 of the screw 14 be in the range of 0.0625to 1.00 to allow the blades 42 to pick-up raw food product therefrom asthe screw 14 and blades 42 rotate past each other. Further in thisregard, it is more preferred that the leading edges 46 have a radiallocation that is just slightly larger than the outer cylindrical surface18, with the radial distance R_(G) being 0.13 inch or less. In one verypreferred embodiment, the radial distance R_(G) is 0.125 inch. Again asbest seen in FIG. 1, each of the wedge-shaped profiles of the blades 42extend axially away from a planar face surface 54 of the blade plate 22that intersects with a conical surface 56 adjacent the leading edges 46of the blades 42. As best seen in FIGS. 2 and 3, in the illustratedembodiment, each of the blades 42 includes a somewhat oval-shaped base55 that extends into the blade plate 22 to mount the blade 42 to theblade plate 22, with only the wedge-shaped profile extending axiallyaway from the surface 54. The surface 54 overlies the extrusion channels28 and acts as a guide surface for the raw food product as it is forcedradially outward through the extrusion channels 28. The surface 54 alsooverlies the planar surface 32, with the relative rotation of the planarsurface 54 relative to the planar surface 32 creating a twist in theextruded food product exiting the extrusion channels 28.

As best seen in FIG. 2, the impeller 26 includes a set of impeller vanes58 (8 in the illustrated embodiment), with each vane 58 having asomewhat crescent shape. As best seen in FIGS. 1 and 2, each of thevanes 58 has a planar face 60 that extends transverse to the axis 16,and leading and trailing side walls 62 and 64 that extend betweenconical surfaces 65 and the planar face 60 and define the crescent shapeof the vane 58.

As best seen in FIG. 1, in the illustrated embodiment, the rotatingplate 22 is a multi-piece assembly and includes a central nose conecomponent 66 defining the impeller 26, a face plate 68 defining theplanar surface 54 and the conical surface 56, a backer plate 70supporting the face plate 68 and the blades 42, a blade retaining plate72, and the blades 42, which are preferably separate pieces made from asuitable material, such as durable steel, with the face plate 68preferably being made from a suitable material, such as brass, ceramic,or cast iron. In this regard, the heat conduction properties of the faceplate material are important.

As best seen in FIG. 1, the nose impeller 24 includes another set ofimpeller vanes 76, with each of the vanes 76 having a planar face 78that extends parallel to the faces 60 of the vanes 58 and transverse tothe axis 16. Preferably, the vanes 76 are crescent shaped similar to thevanes 58, and include leading and trailing side walls that extend fromthe planar face 78 to a conical surface 84 of the end nose 17.

In operation, the feed screw 14 directs raw food product into theannular space 44 where the rotating blades 42 force the raw food productat high pressure into the extrusion channels 28. The high pressure andtemperature generated by the rotation of the blades 42 rotating plate 22relative to the stationary stator plate 20 gelatinizes the raw foodproduct as it forced radially outward to the axial gap between theplaner surfaces 32 and 54. The now gelatinized food product is twistedby the relative rotation between the surfaces 32 and 54 and expands asit radially exits the head assembly 10. The impellers 24 and 26 act torestrict inward radial movement of the raw food product from the annularspace 44 toward the axis 16, thereby minimizing stagnation and/orburning of the raw food product centrally between the nose 17 and therotating plate 22.

The radial locations of the extrusion channels 44, the inner surface 30,the planar surface 32, the blades 42, and the planar surface 54 aregenerally in the range of 2 to 4 times greater than the radial locationsof corresponding features in conventional head assemblies for rotaryhead extruders. The same is true for the features of the feed screw 14.This size increase offers the potential for greater output capacity,which can be realized through the use of the above described features ofthe head assembly 10. In this regard, a test head assembly based on theillustrated embodiment of the head assembly 10 demonstrated a pounds perhour output capacity that was over five times greater than currentconventional rotary head extruders for extruding food product.

It should be appreciated that while a preferred embodiment has beenshown and described herein, not every feature may be required for agiven application and/or it may be desirable to modify some features.For example, while twelve of the blades 42 are shown, in someapplications fewer or more blades may be desired. The same may be truefor the extrusion channels 28 and the vanes 58 and 76. As anotherexample, in some applications, it may be advantageous to employ one ormore of the features disclosed herein in a head assembly that isconventional in size. As yet another example, in some applications, itmay be desirable to employ blades 42 of a more conventional design inconnection with the extrusion channels 28 as disclosed herein, or it maybe desirable to employ the blades 42 as disclosed herein with moreconventional extrusion channels. As another example, in someapplications, it may be desirable to employ vanes 58 or 76 on a moreconventional rotating blade plate or screw.

1. A head assembly for use in a rotary head extruder for extruding afood product, the rotary head extruder including a feed screw mountedfor rotation about an axis to direct raw food product to the headassembly for extrusion thereat, the head assembly comprising: anannular-shaped stator plate including a plurality of circumferentiallyspaced extrusion channels extending outwardly from a radially innersurface centered on the axis; and a rotating blade plate including atleast six circumferentially spaced blades located to extend into anannular space underlying the extrusion channels and the radially innersurface of the stator plate.
 2. The head assembly of claim 1 whereinthere are at least ten of the circumferentially spaced blades.
 3. Thehead assembly of claim 1 wherein there are at least twelve of thecircumferentially spaced blades.
 4. (canceled)
 5. The head assembly ofclaim 1 wherein each of the blades has a wedge-shaped profile thatdiverges from a leading edge to a trailing edge.
 6. The head assembly ofclaim 1 further comprising an impeller located on the end nose of thefeed screw for rotations therewith and surrounded by the stator plate,the impeller including a set of impeller vanes; each of the vanes havinga planer face transverse to the axis.
 7. The head assembly of claim 1further comprising an impeller on the rotating blade plate surrounded bythe blades, the impeller including a set of impeller vanes, each of thevanes having a planer face transverse to the axis.
 8. A head assemblyfor use in a rotary head extruder for extruding a food product, therotary head extruder including a feed screw mounted for rotation aboutan axis to direct raw food product to the head assembly for extrusionthereat, the head assembly comprising: an annular-shaped stator plateincluding a plurality of circumferentially spaced extrusion channelsextending outwardly from a radially inner surface centered on the axis;a first impeller located on the end nose of the feed screw for rotationtherewith and surrounded by the stator plate, the first impellerincluding a first set of impeller vanes, each of the vanes of the firstset having a planer face transverse to the axis; a rotating blade plateincluding a plurality of circumferentially spaced blades located toextend into an annular space underlying the extrusion channels and theradially inner surface of the stator plate; and a second impeller on therotating blade plate surrounded by the blades, the second impellerincluding a second set of impeller vanes, each of the vanes of thesecond set having a planer face that extends parallel to the faces ofthe first set of vanes.
 9. The head assembly of claim 8 wherein thereare at least six of the circumferentially spaced blades.
 10. The headassembly of claim 8 wherein there are at least ten of thecircumferentially spaced blades.
 11. The head assembly of claim 8wherein there are at least twelve of the circumferentially spacedblades.
 12. (canceled)
 13. The head assembly of claim 8 wherein each ofthe blades having a wedge-shaped profile that diverges from a leadingedge to a trailing edge.
 14. A head assembly for use in a rotary headextruder for extruding a food product, the rotary head extruderincluding a feed screw mounted for rotation about an axis to direct rawfood product to the head assembly for extrusion thereat, the headassembly comprising: an annular-shaped stator plate including aplurality of guide walls defining a plurality of extrusion channelsextending outwardly from a radially inner surface centered on the axis,each of the guide walls extending at an angle in the range of 20°-50°from tangent to a circle defined by the inner surface; and a rotatingblade plate including a plurality of circumferentially spaced bladeslocated to extend into an annular space underlying the extrusionchannels and the radially inner surface of the stator plate.
 15. Thehead assembly of claim 14 wherein the angle is in the range of 30°-40°.16. The head assembly of claim 14 wherein there are at least six of thecircumferentially spaced blades.
 17. The head assembly of claim 14wherein there are at least ten of the circumferentially spaced blades.18. The head assembly of claim 14 wherein there are at least twelve ofthe circumferentially spaced blades.
 19. (canceled)
 20. The headassembly of claim 14 wherein each of the blades having a wedge-shapedprofile that diverges from a leading edge to a trailing edge.
 21. Thehead assembly of claim 14 further comprising an impeller located on theend nose of the feed screw for rotations therewith and surrounded by thestator plate, the impeller including a set of impeller vanes; each ofthe vanes having a planer face transverse to the axis.
 22. The headassembly of claim 14 further comprising an impeller on the rotatingblade plate surrounded by the blades, the impeller including a set ofimpeller vanes, each of the vanes having a planer face transverse to theaxis.
 23. (canceled)
 24. (canceled)
 25. (canceled)
 26. (canceled) 27.(canceled)
 28. (canceled)
 29. (canceled)
 30. A head assembly for use ina rotary head extruder for extruding a food product, the rotary headextruder including a feed screw mounted for rotation about an axis todirect raw food product to the head assembly for extrusion thereat, thehead assembly comprising: an annular-shaped stator plate including aplurality of circumferentially spaced extrusion channels extendingoutwardly from a radially inner surface center on the axis; and arotating blade plate including a plurality of circumferentially spacedblades located to extend into an annular space underlying the extrusionchannels and the radially inner surface of the stator plate, each of theblades having a wedge-shaped profile that diverges from a leading edgeto a trailing edge.
 31. The head assembly of claim 30 wherein there areat least eight of the circumferentially spaced blades.
 32. The headassembly of claim 30 wherein there are twelve of the circumferentiallyspaced blades.
 33. The head assembly of claim 30 further comprising animpeller located on the end nose of the feed screw for rotationstherewith and surrounded by the stator plate, the impeller including aset of impeller vanes; each of the vanes having a planer face transverseto the axis.
 34. The head assembly of claim 30 further comprising animpeller on the rotating blade plate surrounded by the blades, theimpeller including a set of impeller vanes, each of the vanes having aplaner face transverse to the axis.
 35. A head assembly for use in arotary head extruder for extruding a food product, the rotary headextruder including a feed screw mounted for rotation about an axis todirect raw food product to the head assembly for extrusion thereat, thehead assembly comprising: an annular-shaped stator plate including aplurality of guide walls defining at least fourteen extrusion channelsextending outwardly from a radially inner surface centered on the axis;and a rotating blade plate including a plurality of circumferentiallyspaced blades located to extend into an annular space underlying theextrusion channels and the radially inner surface of the stator plate.36. The head assembly of claim 35 wherein each of the guide wallsextends at an angle in the range of 20° to 50° from tangent to a circledefined by the inner surface.
 37. The head assembly of claim 35 whereinthe guide walls define no more than twenty-one of the extrusion channelsextending outwardly from the radially inner surface.
 38. A head assemblyfor use in a rotary head extruder for extruding a food product, therotary head extruder including a feed screw which mounts for rotationabout an axis to direct raw food product to the head assembly forextrusion thereat, the head assembly comprising: an end nose located onthe feed screw for rotation therewith, the end nose having an outwardlyfacing cylindrical surface; a rotating blade plate including a pluralityof circumferentially spaced blades located to extend over thecylindrical surface of the end nose, each of the blades having a leadingedge spaced from the cylindrical surface by a radial distance in therange of 0.0625 inch-1.000 inch.
 39. The head assembly of claim 38wherein the radial distance is in the range of 0.0625 inch-0.13 inch.